Severe damage to synchronous condensers, caused by lube failure, demand stricter requirements for the oil system

However, recent incidents have highlighted vulnerabilities in lubrication and oil-lifting systems, prompting a comprehensive review and stricter reliability requirements. The study begins by outlining the importance of lubrication for high-speed 2 pole rotating machines.

Proper lubrication ensures bearing integrity, minimizes friction, dissipates heat, and prevents catastrophic failures. The paper then details two major events, Case A during a blackout test and Case B during normal operation, where loss of lubrication led to extensive mechanical damages. In both cases, failures in emergency oil systems and auxiliary power restoration sequences resulted in bearings operating without oil during machine deceleration, causing severe wear and deformation. The methodology includes root cause analysis of both failures, mechanical inspections, and non-destructive testing (NDT), such as penetrant testing, magnetoscopy, and ultrasonic checks. Post-failure procedures involved dismantling affected components, hardness tests, run-out measurements, and metallurgical evaluations to determine repair feasibility. Case A required complete replacement of the rotor-flywheel assembly due to extreme deformation and contamination, while Case B involved complex restoration processes, including submerged arc welding and thermal treatments, to recover the generator rotor.

The paper also presents corrective actions implemented by Terna, including hardware upgrades

(additional sensors, improved valves, filtration systems) and software modifications to enhance control logic and alarm management. These countermeasures aim to strengthen lubrication reliability during both start-up and emergency conditions. Furthermore, lessons learned emphasize the need for predictive maintenance strategies, improved testing protocols, and strategic spare part management to reduce downtime. Results indicate that both failures caused machine unavailability exceeding one year, significantly impacting grid resilience. The analysis underscores the operational and economic risks associated with lubrication system failures and highlights the necessity of robust design and maintenance practices to ensure long-term reliability of synchronous condensers.